Damping device for moving-coil transformers



Sept. 16, 1969 J. E. LENZ 3,467,928

DAMPING DEVICE FOR MOVING-COIL TRANSFORMERS Filed April 19, 1967 2 Sheets-Sheet l 5 firm/5A" dim/6351677 2 Sheets-Sheet :1

J. E. LENZ DAMPING DEVICE FOR MOVING-COIL TRANSFORMERS Sept. 16, 1969 Filed April 19, 1967 2 fiitnfif: I 4/ z/mes' 25223,

Dy flaw I United States Patent 3,467,928 DAMPING DEVICE FOR MOVING-COIL TRANSFORMERS James E. Lenz, Hendersonville, N.C., assignor to General Electric Company, a corporation of New York Filed Apr. 19, 1967, Ser. No. 632,004 Int. Cl. H01f 21/02 US. Cl. 33640 3 Claims ABSTRACT OF THE DISCLOSURE Moving coil in oil-filled constant-current transformer is provided with projecting fiat paddles to damp excessive motion of the coil which would cause light flicker of gaseous discharge lamps connected to the transformer.

It is an object of the invention to provide moving-coil constant-current transformers of oil-filled type having improved operating performance, especially when used in a series circuit of mercury vapor or similar gaseous discharge lamps.

It is a particular object of the invention to provide a damping device for limiting undesirable movement of the moving coil of the transformer which would otherwise adversely afiect the operation of the lamps or other loads connected thereto and result in other disadvantages.

Other objects and advantages will become apparent from the following description and the appended claims.

With the above objects in view, the present invention relates to a constant-current regulator device comprising, in combination, a container, a dielectric liquid in the container, a moving-coil transformer in the container immersed in the dielectric liquid, the transformer comprising a primary winding and a secondary winding, one of the windings being movable relative to the other winding along a path, and damping means such as a flat board member secured to and movable with the movable winding through the dielectric liquid for damping the movement of the latter winding.

The invention will be better understood from the following description taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a perspective view of a movable-coil transformer embodying a damping device in accordance with the invention;

FIGURE 2 is a view in elevation showing the transformer and damping device in an oil-filled tank;

FIGURE 3 is a plan view of one of the damping members; and

FIGURE 4 is a circuit diagram of a lighting system connected to the moving-coil transformer.

Referring now to the drawings, and particularly to FIGURE 1, there is shown a constant-current transformer 1 comprising a primary winding 2 surrounding and fixed relative to the central leg 3a of core 3, and a secondary winding 4 coaxial with primary winding 2 and mounted on carriage frame 5 slidable on fixed uprights 10, for movement of the secondary winding along core leg 3a toward and away from the primary winding. While in the described embodiment the movable coil is the secondary winding, it will be understood that it may alternatively be the primary winding.

A transformer of the described type is a variable impedance device that provides a constant output current to a range of load impedances throughout a limited variation in the primary supply voltage, and corrects any variations in output current by changing the variable impedance in series with the load. The invention is particularly useful in series lighting circuits of which an example is shown in FIGURE 4, wherein constant-current transformer 1 is connected with its secondary winding 4 in series with a plurality of isolating transformers 6, 6a, 6b having lamps L, typically of gaseous discharge type such as mercury vapor lamps, connected respectively to the secondary windings thereof. On field circuits where sudden changes in line voltage may occur due to heavy, intermittent loads on the system, the floating coil of the constantcurrent transformer may be kept in almost constant oscillating motion, resulting in visible flicker of the connected lamps. It has been found, in the course of tests made in connection with the present invention, that such oscillation is particularly accentuated by gaseous discharge lamps, which have negative resistance characteristics, as compared to filament lamp loads which have positive resistance characteristics and which normally do not cause similar difliculties.

In accordance with the invention, this problem is overcome by attaching damping members 7, 7 (see FIGURE 1) in the form of relatively rigid, flat boards or paddles to the movable supporting frame 5 of moving coil 4, such that the paddle members extend in a plane transverse to the path of movement of the moving coil. In the illustrated embodiment, in which the transformer tank 8 (see FIGURE 2) is generally circular in cross-section paddle members 7, 7', are advantageously arc-shaped as shown in FIGURE 3, so that when attached to carriage frame 5 in laterally projecting position on opposite sides of coil 4, they conform generally to the curvature of tank 8. As seen in FIGURE 1, the paddle members rest at opposite ends on horizontal flanges 5a, 5b of frame 5, to which they are fixedly secured by bolts as shown, or by any other suitable means. Transformer 1 and attached damping paddles 7, 7' are arranged immersed in insulating liquid 9, such as mineral oil, chlorinated diphenyl, or the like, contained in tank 8 as seen in FIGURE 2. In this arrangement, paddles 7, 7' extend laterally beyond the transformer coils in a plane transverse to the path of movement of moving coil 4 in the dielectric liquid as indicated by the arrows. During such operational movement of coil 4, paddles 7, 7' thus provide considerably increased resistance to passage through the dielectric oil, with the result that the coil motion is damped sufiiciently so that normal disturbances on the circuit system do not cause coil excursions large enough to produce visible flicker of lamps L.

It will be evident that the amount of damping resistance can be readily controlled by using paddles of larger or smaller surface area or using an appropriate number of paddles. It will also be understood that the particular configuration of the damping paddles may be varied from that shown while still obtaining the desired damping action.

The described arrangement provides a simple, inexpensive and reliable means for limiting the oscillation or hunting of the moving coil of a constant-current transformer as it shifts position to compensate for changes in line voltage or load impedance. Load current pulsations, which can cause annoying light flicker in the connected light sources, are thereby largely eliminated or minimized. A further advantage is that the dropping of the moving coil when power is removed from the transformer is substantially retarded, thereby avoiding the risk of undue wear or damage to the parts of the transformer attendant on sudden or rapid dropping of the coil.

While the present invention has been described with reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually departing from the scope of the invention. Therefore, the appended claims are intended to cover all such equivalent variations as come within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A current regulator device comprising, in combination, a container, a dielectric fluid in said container, a moving-coil transformer in said container immersed in said dielectric fluid, said transformer comprising a primary winding anda secondary winding, one of said windings being movable relative to the other winding along a path, and damping means secured to and movable with said movable winding through said dielectric fluid for damping the movement of the latter winding, said damping means comprising at least one flat board member projecting transverse said path of movement a substantial distance beyond and about said movable winding.

2. A device as defined in claim 1, said dielectric fluid being a liquid, said damping means comprising a pair of flat board members secured to said movable winding on opposite sides thereof and extending substantially around and laterally beyond said movable winding transversely to said path of movement thereof, whereby said members provide substantial resistance to said dielectric liquid during movement of said movable winding for retarding the motion thereof.

3. A device as defined in claim 2, said fiat board members having a configuration generally conforming to the cross-sectional shape of said container.

References Cited UNITED STATES PATENTS 942,544 12/1909 Clifi 33640 X 988,312 4/1911 Clilf 33640 X 1,493,849 5/ 1924 Eschholz 336-41 2,080,902 5/ 1937 Uyterhoeven et al. 315189 1,389,193 8/1921 Harlow 336-40 JAMES W. LAWRENCE, Primary Examiner C. R. CAMPBELL, Assistant Examiner US. Cl. X.R. 315l89; 3361 17 

